Power-Dividing Device and Axle-Driving Device for a Working Vehicle

ABSTRACT

A power-dividing device for a working vehicle includes a case member, an input shaft supported by the case member so that a first end portion of the input shaft can be operatively connected to a driving source, a PTO unit having a PTO shaft supported by the case member so as to be offset with respect to the input shaft, a power transmission mechanism accommodated in the case member to transmit power from the input shaft to the PTO shaft, and a first pump unit having a first pump shaft operatively connected to the input shaft and being fluid-connected to an actuator disposed outside.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power-dividing device of a workingvehicle that is formed to be able to divide or split a driving powerinput from a driving source into at least two routes.

The invention also relates to an axle-driving device for independentlydriving drive wheels with motor units provided for the respective driveaxles.

2. Related Art

Conventionally, various power transmission structures in workingvehicles have been proposed and employed. For example, there is aconventionally known structure in a working vehicle including a pumpunit operatively connected to a driving source and a driven-sideactuator fluid-connected to the pump unit, in which the actuator isdisposed at a distance from the hydraulic pump.

In this structure, the hydraulic pump unit forms a main powertransmission path for changing a speed of and outputting a driving powerfrom the driving source together with the actuator.

Depending on uses, an auxiliary power transmission path may be requiredin some cases in addition to the main power transmission path in thepower transmission structure including the hydraulic pump unit and theactuator disposed at a distance from each other. An example of thesecases is a lawn mower in which power from a common driving source isdivided or split and output into a traveling power transmission path fordriving drive wheels and a PTO power transmission path for driving awork machine such as a mower.

Cases using a hydraulic motor unit as the actuator will be describedbelow as examples.

There are disclosed, in U.S. Pat. No. 4,395,865 (hereafter, referred toas a cited reference 1) and U.S. Pat. No. 5,809,756 (hereafter, referredto as a cited reference 2), lawn mowers each including a PTO powertransmission path for transmitting power from an engine to a mower inaddition to a traveling power transmission path formed of a hydraulicpump unit operatively connected to the engine and a hydraulic motor unitdisposed at a distance from the hydraulic pump unit to drive drivewheels.

More specifically, in the lawn mower described in the cited reference 1,first and second output shafts are provided to the engine as a commondriving source and are operatively connected to the hydraulic pump unitand the mower, respectively. In other words, in the lawn mower describedin the cited reference 1, the traveling power transmission path and thePTO power transmission path are completely separate from each other.

However, because the traveling power transmission path and the PTO powertransmission path are completely separate from each other in thisstructure, the number of parts forming the power transmission pathsincreases and, also, large space for accommodating both the powertransmission paths is required. actuator and a hydraulic motor unitfluid-connected to the hydraulic pump unit as the motor unit.

Each of the axle-driving devices described in U.S. Pat. No. 4,920,733(hereafter, referred as cited reference 3) and Japanese Utility ModelUnexamined Publication No. 56-77437 (hereafter, referred as a citedreference 4) has an advantage that a cornering ability and, especially,an ability to make a small turn of a vehicle can be improved because therespective drive axles can be independently driven at changeable speeds.However, they are susceptible to improvement with regard tominiaturization of the whole units.

Especially, it is preferable to provide a brake unit to each drive axleso as to enable the vehicle to make a smaller turn. However, neither ofthe cited references mentions the brake unit and, of course, there is nodescription of miniaturization of the whole unit including the brakeunit.

The present invention has been accomplished in view of the above relatedart, and it is an object of the invention to provide a power-dividingdevice of a working vehicle, that is capable of dividing or splitting adriving power input from a driving source into a main power transmissionpath including a pump unit and an auxiliary power transmission pathincluding a PTO unit with a simple structure.

The present invention has been accomplished in view of the above relatedart, and it is another object of the invention to miniaturize a wholeunit in the axle-driving device having a motor unit and a brake unit foreach drive axle.

It is still another object of the invention to secure large and free

Moreover, in such a power transmission structure having the two powertransmission paths, power transmission/interruption in each powertransmission path needs to be independently controlled.

In this regard, electromagnetic clutches for powertransmission/interruption are inserted into the respective powertransmission paths in the lawn mower described in the cited reference 1,but there is a problem in that the electromagnetic clutches are of poordurability and, as a result, impair reliability of the powertransmission paths.

On the other hand, in the lawn mower described in the cited reference 2,a common output shaft is provided to the engine and a pulley for thedrive wheels and a pulley for the mower are supported on the commonoutput shaft to thereby divide or split power from the common outputshaft into the traveling power transmission path and the PTO powertransmission path.

In this structure, however, there is a problem in that the common outputshaft has to be made long and a large load is applied to the commonoutput shaft.

Further, there is no description of how to transmit/interrupt power inthe respective power transmission paths in the cited reference 2.

There are also conventionally known axle-driving devices in each ofwhich a motor unit forming a non-stepwisely changeable transmission suchas a hydrostatic transmission (hereafter, referred to as a HST) incooperation with a drive-side actuator is provided to each a drive axle.

The conventional axle-driving devices will be described by taking cases,as examples, each using a hydraulic pump unit as the drive-side spacebetween drive wheels without increasing a distance between the drivewheels in a vehicle including the axle-driving device having the motorunit and the brake unit for each drive axle.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided apower-dividing device for a working vehicle that includes a case member,an input shaft supported by the case member so that a first end portionof the input shaft can be operatively connected to a driving source, aPTO unit having a PTO shaft supported by the case member so as to beoffset with respect to the input shaft, a power transmission mechanismaccommodated in the case member to transmit power from the input shaftto the PTO shaft, and a first pump unit having a first pump shaftoperatively connected to the input shaft and being fluid-connected to anactuator disposed outside.

With this structure, the driving power from the driving source caneasily be divided or split into a main power transmission path includingthe pump shaft and an auxiliary power transmission path including thePTO shaft.

Especially, when the output from the PTO shaft is transmitted to theground work machine, it is possible to suppress a vertical distancebetween the PTO shaft and the input portion of the ground work machinewhile suppressing a vertical distance between the output portion of thedriving source and the input shaft. It is therefore possible to carryout power transmission between the driving source and the input shaftand between the PTO shaft and the ground work machine without laboring.

For example, the first pump shaft may be operatively connected to theinput shaft through the power transmission mechanism.

Furthermore, the first pump shaft may be disposed between the inputshaft and the PTO shaft in a vertical direction In one embodiment, thepower-dividing device further include a second pump unit which has asecond pump shaft operatively connected to the input shaft and which isfluid-connected to the actuator disposed outside.

In the one embodiment, for example, the second pump shaft is operativelyconnected to the input shaft through the power transmission mechanism.

Preferably, the first and second pump units are formed of the samecomponents.

With this structure, it is possible to use general-purpose products asthe first and second pump units.

In the one embodiment, the input shaft is disposed along a vehicle backand forth direction, and the first pump unit and the second pump unitmay be coupled to the same side of the case member in the vehicle backand forth direction.

Alternatively, the first pump unit and the second pump unit may becoupled to a first side and a second side of the case member in thevehicle back and forth direction, respectively.

With this structure, it is possible to effectively utilize an idle spacein the vicinity of the case member.

In the alternative structure, preferably, the first and second pumpshafts are disposed coaxially.

In the one embodiment, for example, the first and second pump unitsrespectively may include first and second pump cases coupled to the casemember, first and second pump main bodies accommodated in the first andsecond pump cases, and first and second center sections supporting thefirst and second pump main bodies. Each of the first and second pumpcases includes a proximal end wall having a through hole through whichthe corresponding pump shaft is inserted and a peripheral wall extendingin an axial direction of the corresponding pump shaft from a peripheraledge portion of the proximal end wall and having an opening on a freeend side. The proximal end wall is coupled to the case member. Each ofthe first and second pump main bodies is driven by the correspondingpump shaft and is accommodated into the corresponding pump case from theopening on the free end side of the corresponding pump case. The firstand second center sections are coupled to the first and second pumpcases, respectively, so as to close the opening on the free end sides ofthe first and second pump cases.

Furthermore, the working vehicle may include a pair of left and rightdrive wheels and a ground work machine. In that case, for example, thepower-dividing device is disposed between the driving source and theground work machine in the vehicle back and forth direction. The inputshaft is operatively connected to an output portion of the drivingsource. The PTO shaft is operatively connected to the ground workmachine. The first and second pump units are fluid-connected to a pairof left and right hydraulic motor units and for driving the pair ofdrive wheels, respectively

In the one embodiment, preferably, the power-dividing device further hasa charge pump unit operatively connected to the input shaft.

With this structure, it is possible to efficiently obtain hydraulicfluid for various hydraulic devices.

Preferably, the PTO unit further includes a PTO clutch mechanism forselectively engaging/interrupting power transmission from the inputshaft to the PTO shaft.

More preferably, the PTO unit further includes a PTO brake mechanism forreleasing/applying a braking force from and to the PTO shaft insynchronization with an operation for transmitting/interrupting powerfrom the input shaft to the PTO shaft by the PTO clutch mechanism.

For example, a part of pressure oil from the charge pump unitoperatively driven by the input shaft is supplied to the PTO clutchmechanism and/or the PTO brake mechanism as hydraulic fluid.

In any one of the above embodiments, the input shaft and the PTO shaftare, for example, along the vehicle back and forth direction and aredisposed substantially in the same position in a vehicle widthdirection.

According to one aspect of the present invention, there is furtherprovided a power-dividing device that includes a case member, an inputshaft supported by the case member so that a first end portion of theinput shaft can be operatively connected to a driving source, a PTOshaft supported by the case member so as to be offset with respect tothe input shaft, a power transmission mechanism accommodated in the casemember to transmit power from the input shaft to the PTO shaft, a firstpump shaft operatively connected to the input shaft, and a first pumpunit main body accommodated in the case member, driven by said firstpump shaft and fluid-connected to an actuator disposed outside.

According to another aspect of the present invention, there is providedan axle-driving device that has an axle case including an outer wallsupporting a drive axle in a rotatable manner about its axis and aninner wall separated inward in a vehicle width direction from the outerwall so that an inner end portion of the drive axle in the vehicle widthdirection is positioned between the outer wall and the inner wall, amotor unit forming a non-stepwisely changeable transmission incooperation with an actuator disposed at a distance and including amotor shaft supported by the inner wall in a rotatable manner about itsaxis so that an outer end portion of the motor shaft in the vehiclewidth direction is positioned in a accommodating space in said axle caseand a motor main body supported by said inner wall, a reduction powertransmission unit including an output gear supported on the outer endportion of the motor shaft in the vehicle width direction so as to benon-rotatable with respect to the motor shaft, a final gear supported onthe inner end portion of the drive axle in the vehicle width directionso as to be non-rotatable with respect to the drive axle and a geartrain for reducing a speed of and transmitting power from said outputgear to said final gear and including an intermediate shaft supported bythe axle case so as to be positioned above the motor shaft, and a brakeunit for selectively applying a braking force to the intermediate shaftbased on operation from outside. The motor unit is disposed so that atleast a portion of the motor unit overlaps with the final gear whenviewed along an axial direction of the drive axle. The brake unit issupported by the inner wall of the axle case so as to be positionedabove the motor unit.

With this structure, it is possible to make the unit itself compact.

Especially, a size of a free space between the drive wheels can beincreased without increasing a distance between the drive wheels ascompared with a structure in that the motor unit and the brake unit arearranged in parallel with each other in the vehicle width direction. Itis therefore possible to effectively prevent interference with othermembers such as a center discharge duct which can be provided in abottom portion of the vehicle.

Preferably, the brake unit is disposed so that at least a portion of thebrake unit overlaps with the hydraulic motor unit in plan view.

More preferably, the axle-driving device further includes a mountingstay having a proximal end portion coupled to a body frame and a distalend portion supporting the axle case.

In this embodiment, the mounting stay is formed so as to define asurrounded space in which the motor unit is positioned and at least anupper side of which is open between the inner wall of said axle case andthe body frame. the brake unit includes a rotary member supported on theintermediate shaft in a non-rotatable manner, a fixed member supportedby the axle case, a friction braking device which has a pair of frictiondiscs respectively supported by the rotary member and the fixed memberin a non-rotatable manner and which selectively applies a braking forceto the rotary member based on operation from outside, and an operatingarm for operating the friction braking device by swinging about a pivotaxis disposed in parallel to the intermediate shaft. The operating armcan be operated from the upper opening of the surrounded space.

With this structure, it is possible to easily gain access to theoperating arm in the brake unit through the upper opening. It istherefore possible to simplify the linkage interlocked with and linkedto the operating arm.

More preferably, the motor unit is formed so that a connection portionto the actuator is oriented upward at a position between the operatingarm of the brake unit and the body frame.

With this structure it is possible to simplify the connection member forconnection between the motor unit and the actuator.

For example, the actuator is a hydraulic pump unit. The motor unit is ahydraulic motor unit fluid-connected to the hydraulic pump unit througha flow path so as to form an HST in cooperation with the hydraulic pumpunit. The hydraulic motor unit has a center section formed with an oilpath which forms a portion of the flow path and a first end portion ofwhich forms the connection portion to the actuator.

According to another aspect of the present invention, there is furtherprovided an vehicle that has a body frame including a pair of mainframes disposed along a vehicle back and forth direction, an enginesupported on the body frame, a power-dividing device including a pair ofhydraulic pump units operatively connected to an output portion of theengine, a pair of drive axles, and a pair of axle-driving devicesrespectively and independently driving the pair of drive axles.

In the vehicle of the present invention, each of the pair ofaxle-driving devices includes an axle case, a hydraulic motor unit, areduction power transmission unit and a brake unit.

The axle case has an outer wall supporting the corresponding drive axlein a rotatable manner and an inner wall separated inward in a vehiclewidth direction from the outer wall so that an inner end portion of thedrive axle in the vehicle width direction is positioned between theouter wall and the inner wall. The axle case is supported by thecorresponding main frame.

The hydraulic motor unit is fluid-connected to the correspondinghydraulic pump unit through a flow path so as to form an HST. Thehydraulic motor unit includes a motor shaft supported by the inner wallin a rotatable manner so that an outer end portion of the motor shaft inthe vehicle width direction is positioned in an accommodating space inthe axle case and a motor main body supported by the inner wall.

The vehicle of the present invention further has a reduction powertransmission unit that includes an output gear supported on an outer endportion of the motor shaft in the vehicle width direction in anon-rotatable manner, a final gear supported on an inner end portion ofthe drive axle in the vehicle width direction in a non-rotatable manner,and a gear train for reducing a speed of and transmitting power from theoutput gear to the final gear. The gear train included an intermediateshaft supported by the axle case so as to be positioned above said motorshaft.

The brake unit is formed to selectively apply a braking force to theintermediate shaft based on operation from outside.

The hydraulic motor unit is disposed so that at least a portion of themotor unit overlaps with the final gear when viewed along an axialdirection of said drive axle.

The brake unit is supported by the inner wall of the axle case so as tobe positioned above the hydraulic motor unit.

Preferably, each of the pair of axle-driving devices further includes amounting stay having a proximal end portion coupled to the correspondingmain frame and a distal end portion supporting the axle case. Themounting stay is formed so as to define a surrounded space in which thehydraulic motor unit is positioned and at least an upper side of whichis open between the inner wall of the axle case and the correspondingmain frame. The brake unit includes a rotary member supported on theintermediate shaft in a non-rotatable manner, a fixed member supportedby the axle case, a friction braking device which has friction discsrespectively supported by the rotary member and the fixed member in anon-rotatable manner and which selectively applies a braking force tothe rotary member based on operation from outside, and an operating armfor operating the friction braking device by swinging about a pivot axisdisposed in parallel to the intermediate shaft. The operating arm can beoperated from the upper opening of the surrounded space.

More preferably, the hydraulic motor unit has a center section formedwith an oil path forming a portion of the flow path between thehydraulic pump unit and the hydraulic motor unit. The oil path opensupward at a position between the operating arm in the brake unit and themain frame.

BRIEF DESCRIPTION OF THE DRAWINNGS

The above, and other objects, features and advantages of the presentinvention will become apparent from the detailed description thereof inconjunction with the accompanying drawings wherein.

FIGS. 1(a) and 1(b) are respectively a side view and a plan view of alawn mower, to which a power-dividing device according to one embodimentof the present invention has been applied.

FIG. 2 is an oil hydraulic circuit diagram of the lawn mower shown inFIG. 1.

FIG. 3 is a sectional view taken along line III-III in FIG. 1(a).

FIG. 4 is a vertical sectional side view of the power-dividing deviceshown in FIG. 1.

FIG. 5 is a horizontal sectional plan view of the power-dividing deviceshown in FIG. 4.

FIG. 6 is a back view of the power-dividing device shown in FIGS. 4 and5 with some part of them shown in vertical section.

FIGS. 7(a) and 1(b) are respectively a side view and a plan view ofanother type of lawn mower, to which a power-dividing device accordingto the one embodiment of the present invention has been applied.

FIGS. 8(a) and (b) are back views of modified power-dividing devicesshown in FIG. 6.

FIG. 9 is a back view of another modified power-dividing device shown inFIG. 6.

FIG. 10 is a partial vertical sectional side view of a power-dividingdevice according to another embodiment of the present invention.

FIG. 11 is a schematic side view of a vehicle to which an axle-drivingdevice according to one embodiment of the present invention has beenapplied.

FIG. 12 is a schematic plan view of the vehicle shown in FIG. 11.

FIG. 13 is a schematic back view of the vehicle shown in FIGS. 11 and12.

FIG. 14 is an oil hydraulic circuit diagram of one part of the vehicleshown in FIGS. 11-13.

FIG. 15 is an oil hydraulic circuit diagram of another part of thevehicle shown in FIGS. 11-13.

FIG. 16 is a developed plan view of the power-dividing device of thevehicle shown in FIGS. 11-13.

FIG. 17 is a back view of the power-dividing device of the vehicle shownin FIGS. 11-13.

FIG. 18 is a vertical sectional back view of the axle-driving deviceshown in FIGS. 11-13.

FIG. 19 is a plan view of the axle-driving device shown in FIG. 18.

FIG. 20 is an exploded perspective view of the axle-driving device shownin FIGS. 18 and 19.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

A preferred embodiment of a power-dividing device according to oneaspect of the present invention will be described below with referenceto the accompanying drawings.

A power-dividing device 1A according to one aspect of the invention isformed to be able to divide or split and output a driving power from adriving source 150 into a main power transmission path including pumpunits and driven actuators fluid-connected to each other and anauxiliary power transmission path including a PTO unit.

In this embodiment, a case using first and second hydraulic motor unitsformed to be able to respectively drive a pair of drive wheels as thedriven actuators will be described as an example.

FIGS. 1(a) and 1(b) are a side view and a plan view of a lawn mower 100to which the power-dividing device 1A according to this embodiment isapplied. FIG. 2 is an oil hydraulic circuit diagram of the lawn mower100. FIG. 3 is a sectional view taken along line III-III in FIG. 1(a).

First, the lawn mower 100 will be described.

As shown in FIGS. 1(a) and 1(b), the lawn mower 100 includes a bodyframe 110, a pair of left and right drive wheels (rear wheels in thisembodiment) 120 supported on the body frame 110, casters 130 supportedon the body frame 110 so as to be disposed on one side (front side inthis embodiment) in a back and forth direction of the vehicle withrespect to the drive wheels 120, a ground work machine (mower in thisembodiment) 140 supported by the body frame 110 so as to be positionedbetween the drive wheels 120 and the casters 130, a driving source 150supported on the body frame 110 so as to be positioned on an oppositeside (rear side in this embodiment) of the drive wheels 120 to theground work machine 140 along the back and forth direction of thevehicle, first and second hydraulic motor units 160 a and 160 b havingmotor shafts 161 operatively connected to the pair of left and rightdrive wheels 120, respectively, and the power-dividing device 1Aaccording to this embodiment.

A reference numeral 145 in FIG. 3 denotes a rear discharge duct forminga discharge path from the mower 140. A reference numeral 110 a in FIGS.1(b) and 3 denotes a cross member for reinforcement that is laid acrossand fixed to a pair of left and right main frames forming the body frame110 by welding.

Reference numerals 165 in FIGS. 2 and 3 denote braking devices forapplying braking forces to the motor shafts of the first and secondhydraulic motor units, respectively.

FIGS. 4 and 5 are a vertical sectional side view and a horizontalsectional plan view of the power-dividing device 1A according to thisembodiment, respectively.

As shown in FIGS. 4 and 5, the power-dividing device 1A includes a casemember 10, an input shaft 20 supported by the case member 10, a PTO unit30 accommodated in the case member 10, and a power transmissionmechanism 50 housed in the case member 10 to transmit power from theinput shaft 20 to the PTO shaft 30, a first pump unit 60 a supported bythe case member 10, and a second pump unit 60 b supported by the casemember 10.

As shown in FIGS. 4 and 5, in this embodiment, the case member 10 can bedivided into a first case member 11 and a second case member 12respectively on a first side and a second side in the back and forthdirection of the vehicle.

The input shaft 20 is supported by the case member 10 in such a mannerthat its first end portion 21 (rear end portion in this embodiment) isoperatively connected to the driving source 150.

It is preferable that the input shaft 20 is supported on the case member10 to be positioned substantially in the same position in a verticaldirection as an output portion of the driving source 150 (see FIG.1(a)).

It is more preferable that the input shaft 20 is positionedsubstantially in the same position in a vehicle width direction as theoutput portion of the driving source 150 (see FIG. 1(b)).

With this structure, it is possible to readily couple the output portionof the driving source 150 and the input shaft 20 to each other.

In this embodiment, the driving source 150 is supported in avibration-preventing manner with respect to the body frame 110 and thecase member 10 is fixedly supported on the body frame 110.

Therefore, in order to absorb a vibration difference between the inputshaft 20 and the driving source 150, the input shaft 20 and the outputportion of the driving source 150 are coupled to each other throughvibration absorbing power transmission means. In this embodiment, apower transmission shaft 80 mounted at opposite end portions thereofwith universal joints 81 is used as the vibration absorbing powertransmission means.

Although the case member 10 is fixedly supported on the body frame 110in the state where the case member 10 is disposed at a distance from thedriving source 150 supported on the body frame 110 in avibration-preventing manner in this embodiment, instead, it is alsopossible to couple and support the case member 10 onto the drivingsource 150 in the state where the case member 10 is freely from the bodyframe 110.

With this structure, it is possible to eliminate the vibrationdifference between the driving source 150 and the case member 10.

In this embodiment, the input shaft 20 is supported on the case member10 along the back and forth direction of the vehicle and a second endportion 22 (front end portion in this embodiment) of the input shaft 20positioned on an axial opposite side to the first end portion 21 alsoextends outside from the case member 10 in addition to the first endportion 21 operatively connected with the driving source 150 (see FIG.4).

A charge pump unit 90 is drivably supported on the second end portion 22of the input shaft 20.

The charge pump unit 90 supplies pressure oil to various oil hydrauliccircuits as described later.

Although the charge pump 90 is a trochoid pump in this embodiment, itmay be an external gear pump when high pressure or a large displacementis required.

The PTO unit 30 has a PTO shaft 31. The PTO shaft 31 is supported by thecase member 10 at a position below the input shaft 20.

The PTO shaft 31 is supported by the case member 10 in such a mannerthat a proximal end portion (rear end portion in this embodiment) of thePTO shaft 31 is positioned in the case member 10 and that a free endportion (front end portion in this embodiment) of the PTO shaft 31extends outside from the case member 10.

In this embodiment, the portion of the PTO shaft 31 extending outside isoperatively connected to an input portion of the mower 140 through thevibration absorbing power transmission means 80 (see FIGS. 1(a) and1(b)).

The power transmission mechanism 50 is formed to transmit the drivingpower from the input shaft 20 to the PTO shaft 31 as described above.

In this embodiment, the power transmission mechanism 50 includes adrive-side gear 51 supported on the input shaft 20 so as to benon-rotatable with respect to the input shaft 20, a counter gear 52engaged with the drive-side gear 51, a counter shaft 53 for supportingthe counter gear 52, a driven-side gear 54 engaged with the counter gear52 and formed to be able to transmit rotating power to the PTO shaft 31.

FIG. 6 is a vertical sectional back view of the power-dividing device1A.

As shown in FIG. 6, in this embodiment, the input shaft 20 and the PTOshaft 31 are positioned substantially in the same position in thevehicle width direction and the counter shaft 53 is positionedsubstantially in the same position as the input shaft 20 and the PTOshaft 31 in the vehicle width direction. With this structure, a verticaldistance between the input shaft 20 and the PTO shaft 31 could bemaximized and a length of the power-dividing device 1A in the vehiclewidth direction could be minimized.

It is more preferable that the PTO unit 30 has a PTO clutch mechanism 40for selectively engaging/interrupting power transmission between thedriven-side gear 54 and the PTO shaft 31.

In other words, the driven-side gear 54 may be formed to be rotatablewith respect to the PTO shaft 31 and the PTO clutch mechanism 40 may beprovided between the driven-side gear 54 and the PTO shaft 31.

Specifically, the PTO clutch mechanism 40 includes a drive-side member40 a which is supported on the PTO shaft 31 so as to be rotatable andaxially non-slidable with respect to the PTO shaft 31 and which rotatesintegrally with the driven-side gear 54, a drive-side friction disc 40 bsupported on the drive-side member 40 a so as to be non-rotatable andaxially slidable with respect to the member 40 a, a driven-side member40 c supported on the PTO shaft 31 so as to be non-rotatable withrespect to the PTO shaft 31, a driven-side friction disc 40 d supportedon the driven-side member 40 c so as to be non-rotatable and axiallyslidable in a certain range with respect to the driven-side member 40, aclutch actuating member 40 e for bringing the driven-side friction disc40 d and the drive-side friction disc 40 b into frictional engagementwith each other by receiving hydraulic pressure, and a clutch biasingmember 40 f for separating the clutch actuating member 40 e from thedrive-side friction disc 40 b and the driven-side friction disc 40 d.

By forming the PTO clutch mechanism 40 such that power can beinterrupted between “the drive-side member 40 a rotatable integrallywith the driven-side gear 54 and supported on the PTO shaft 31 so as tobe rotatable with respect to the PTO shaft 31” and “the PTO shaft 31” asdescribed above, it is possible to interrupt power transmission from theinput shaft 20 to the PTO shaft 31 while maintaining power transmissionfrom the input shaft 20 to first and second pump shafts 61 a and 61 bwhich will be described later.

The PTO clutch mechanism 40 with such a structure transmits power fromthe input shaft 20 to the PTO shaft 31 through the drive-side member 40a and the driven-side member 40 c when the clutch actuating member 40 ebrings both the friction discs 40 b and 40 d into frictional engagementwith each other by the action of hydraulic fluid pressure, andinterrupts transmission of power from the input shaft 20 to the PTOshaft 31 when the action of the hydraulic pressure is not received.

As hydraulic fluid to the PTO clutch mechanism, the pressure oil fromthe charge pump can be utilized (see FIG. 2).

It is more preferable that the PTO unit 30 includes a PTO brakemechanism 45 for operating in conjunction with clutch operation of thePTO clutch mechanism 40. Thus, it is possible to effectively prevent thePTO shaft 31 from continuously rotating due to an inertial force of theconnected ground work machine 140 even when the PTO clutch mechanism 40interrupts power transmission.

The PTO brake mechanism 45 includes a brake disc 45 a supported on thePTO shaft 31 so as to be non-rotatable and axially slidable with respectto the PTO shaft 31, a fixed disc 45 b facing the brake disc 45 a so asto be non-rotatable and axially slidable, and a brake actuating member45 c operatively connected to the clutch actuating member 40 e throughan connecting member 42.

The brake actuating member 45 c is operatively connected to the clutchactuating member 40 e in such a manner as to bring the brake disc 45 aand the fixed disc 45 b into frictional engagement with each other whenthe clutch actuating member 40 e is separated from the drive-sidefriction disc 40 b and the driven-side friction disc 40 d by a biasingforce of the clutch biasing member 40 f and in such a manner as to moveaway from the brake disc 45 a and the fixed disc 45 b when the clutchactuating member 40 e receives the action of hydraulic pressure to bringthe drive-side friction disc 40 b and the driven-side friction disc 40 dinto frictional engagement with each other against the biasing force ofthe clutch biasing member 40 f.

As shown in FIG. 2, the first and second pump units 60 a and 60 b arerespectively fluid-connected to the first hydraulic motor unit 160 a andthe second hydraulic motor unit 160 b through oil hydraulic circuits (apair of hydraulic lines 200 a and a pair of hydraulic lines 200 b inthis embodiment).

In other words, in this embodiment, the first pump unit 60 a and thefirst hydraulic motor unit 160 a form a first HST and the second pumpunit 60 b and the second hydraulic motor unit 160 b form a second HST.

Although the power-dividing device 1A according to this embodimentincludes the first and second pump units 60 a and 60 b corresponding tothe pair of left and right hydraulic motor units 160 a and 160 b,respectively, so as to be able to drive the pair of drive wheels 120 ofthe lawn mower 100 at independent rotation speeds of each other, theinvention is not limited to this form but also includes a form havingonly one pump unit and a form having three or more pump units.

For example, if only one pump unit is provided, the single pump unit isfluid-connected to the pair of left and right hydraulic motor units 160a and 160 b through oil hydraulic circuits having fluid distributingmeans such as a flow diverter valve.

At least one of the first pump unit 60 a and the first hydraulic motorunit 160 a forming the first HST and at least one of the second pumpunit 60 b and the second hydraulic motor unit 160 b forming the secondHST are of a variable displacement type in which a suction/dischargerate is changed by operation of an output adjusting member, andnon-stepwisely changeable outputs are obtained from motor shafts of thehydraulic motor units 160 a and 160 b by controlling a slanting positionof the output adjusting member. In this embodiment, the first and secondpump units 60 a and 60 b are of the variable displacement type and thefirst and second hydraulic motor units 160 a and 160 b are of a fixeddisplacement type.

Specifically, the first and second pump unit 60 a and 60 b respectivelyinclude first and second pump shafts 61 a and 61 b operatively connectedto the input shaft 20, first and second pump cases 62 a and 62 b coupledto the case member 10, first and second pump main bodies 63 a and 63 bdriven by the first and second pump shafts 61 a and 61 b, and first andsecond center sections 64 a and 64 b supporting the first and secondpump main bodies 63 a and 63 b.

In this embodiment, the first and second pump units 60 a and 60 b arecoupled to a first side and a second other side of the case member 10 inthe back and forth direction of the vehicle.

Specifically, the first pump unit 60 a is coupled to the first side(front side in this embodiment) of the case member 10 in the back andforth direction of the vehicle so as to be positioned above the PTOshaft 31.

On the other hand, the second pump unit 60 b is coupled to the secondside (rear side in this embodiment) of the case member 10 in the backand forth direction of the vehicle so as to be positioned below thefirst end portion (rear end portion in this embodiment) of the inputshaft 20.

By separately disposing the first and second pump units 60 a and 60 b onthe front and rear sides of the case member 10 along the vehicle backand forth direction, it is possible to make effective use of idle spacesin the vicinity of the input shaft 20 and the PTO shaft 31 to therebysuppress upsizing of the whole power-dividing device.

The first and second pump shafts 61 a and 61 b are supported by the casemember 10 along the back and forth direction of the vehicle,respectively, in such a manner that proximal end portions of the firstand second pump shafts 61 a and 61 b are operatively connected to theinput shaft 20 in the case member 10 and free end portions (or distalend portions) thereof are positioned outside of the case member 10.

Specifically, the counter shaft 53 of the power transmission mechanism50 is not rotatable with respect to the counter gear 52 and is a hollowshaft having an axial hole provided with a spline on an inner peripheralface of the hole.

The first and second pump shafts 61 a and 61 b are disposed coaxiallywith the counter shaft 53, and the respective proximal end portions ofthe first and second pump shafts 61 a and 61 b are coupled to the splineformed on the inner surface of the counter shaft 53.

By coaxially disposing the first and second pump shafts 61 a and 61 b,it is possible to efficiently transmit power from the input shaft 20 tothe first and second pump shafts 61 a and 61 b.

The first and second pump cases 62 a and 62 b respectively includeproximal end walls having through holes through which the first andsecond pump shafts 61 a and 61 b are inserted, and peripheral wallsextending in the axial direction of the first and second pump shaftsfrom peripheral edge portions of the proximal end walls so as to have anopening on free end sides. The proximal end walls are coupled to thecase member 10.

The first and second pump main bodies 63 a and 63 b respectively includepiston units 66 a and 66 b which rotate about axes of the correspondingpump shafts and reciprocate along the axes as the first and second pumpshafts 61 a and 61 b rotate about the axes, cylinder blocks 67 a and 67b which accommodate the piston units 66 a and 66 b in an axiallyslidable manner and which rotate with the piston units 66 a and 66 babout the axes of the corresponding pump shafts, output adjustingmembers 68 a and 68 b which determine stroke lengths of the piston units66 a and 66 b according to slanting positions to changesuction/discharge rate by the piston units 66 a and 66 b, and controlshafts 69 a and 69 b coupled with the output adjusting members 68 a and68 b so as to be able to control the slanting positions of the outputadjusting members 68 a and 68 b from outside.

Although the hydraulic pump main bodies 63 a and 63 b are of anaxial-piston type in this embodiment, it is needless to say that theymay be of a radial-piston type.

As described above, in the power-dividing device IA according to thisembodiment, the first and second pump units 60 a and 60 b are formed ofthe same members and are coupled to the case member 10.

Therefore, common general-purpose products can be used as the first andsecond pump units 60 a and 60 b to thereby reduce the cost inproduction.

It is preferable that the first and second hydraulic pump main bodies 63a and 63 b are coupled to the case member 10 so that the control shafts69 a and 69 b of the respective main bodies 63 a and 63 b extend on afirst side and a second side in the vehicle width direction.

With this structure, the respective control shafts 69 a and 69 b of thefirst and second hydraulic pump main bodies 63 a and 63 b can be readilyconnected to left and right operating levers 190 a and 190 b (FIG. 1(a))disposed in the vicinity of a driver's seat, respectively.

The first and second center sections 64 a and 64 b are coupled to thefirst and second pump cases 62 a and 62 b, respectively, so as to closethe free-end-side openings of the first and second pump cases 62 a and62 b in the state of supporting the first and second cylinder blocks 67a and 67 b in a rotatable and slidable manner.

The first and second center sections 64 a and 64 b are respectivelyprovided with a pair of first oil paths 210 a and a pair of second oilpaths 210 b forming portions of the pair of first hydraulic lines 200 aand the pair of second hydraulic lines 200 b, first and second bypassoil paths 220 a and 220 b respectively fluid-connecting the pair offirst oil paths 210 a and connecting the pair of second oil paths 210 b,check valves 230 a and 230 b inserted into the first and second bypassoil paths 220 a and 220 b, and a charge oil path 240 a forming a chargeline from the charge pump 90 to the pair of first oil paths 210 a andthe pair of second oil paths 210 b (see FIG. 2).

It is preferable that the first and second center sections 64 a and 64 bare respectively provided with other bypass oil paths 250 a and 250 bwhich can forcibly connect the pair of first oil paths 210 a andconnecting the pair of second oil paths 210 b.

By providing these other bypass oil paths 250 a and 250 b, it ispossible to readily obtain a freewheeling state in forcibly towing thevehicle in the event of failure and the like of the driving source.

In this embodiment, the hydraulic motor units 160 a and 160 b arerespectively disposed on an upper face of reduction gear boxes 162 sothat the motor shafts 161 are orthogonal to the corresponding axles 121as shown in FIG. 3 to thereby save spaces between the body frame 110 andthe drive wheels 120.

Specifically, an inner face in the vehicle width direction of each thereduction gear box 162 is fastened to the body frame 110 and an outerface in the vehicle width direction of each the reduction gear box 162supports the axle 121 in a projecting manner, the drive wheel 120 beingmounted to the axle 121.

The hydraulic motor units 160 a and 160 b are disposed on the reductiongear boxes 162 with the above structures so that the motor shafts 161are orthogonal to the axles 121.

Although the hydraulic motor units 160 a and 160 b are disposed on theupper faces of the reduction gear boxes 162 so that the motor shafts 161are oriented in the vertical direction in the form shown in the figures,instead, it is also possible to dispose the hydraulic motor units 160 aand 160 b on front faces or rear faces of the reduction gear boxes 162so that the motor shafts 161 are oriented in the horizontal direction.

In each reduction gear box 162, an intermediate shaft 163 is rotatablydisposed so as to be positioned concentrically with the correspondingaxle 121. Fixed to the intermediate shaft 163 is a large bevel gear 164b engaged with a small pinion 164 a provided to the corresponding motorshaft 161 so as to convert power rotation from the motor shaft 161 intoperpendicular one of and transmit the power rotation with reducing itsspeed. Further, a reduction gear 166 of a planet-gear type is insertedinto a portion where the intermediate shaft 163 and the correspondingaxle 121 butt to each other.

With this structure, the speed of the power output from the hydraulicmotor unit 160 is reduced in two steps as a whole by the reduction gearbox 162 and drives the drive wheel 120.

With reference mainly to FIG. 2, the oil hydraulic circuit of thepower-dividing device 1A according to this embodiment will be describedbelow.

A suction port of the charge pump 90 is fluid-connected to an oil tank180 through a filter 181 and a discharge port thereof is fluid-connectedto a first HST oil hydraulic circuit 300 a, a second HST oil hydrauliccircuit 300 b, a mower lifting/lowering oil hydraulic circuit 300 c andthe PTO clutch mechanism oil hydraulic circuit 300 d.

Specifically, a main discharge line 310 into which a main relief valve320 is inserted is connected to the discharge port of the charge pump90.

Hydraulic fluid is supplied to the mower lifting/lowering oil hydrauliccircuit 300 c from a primary side of the main relief valve 320.

For the first HST oil hydraulic circuit 300 a and the second HST oilhydraulic circuit 300 b, the hydraulic fluid is supplied to the chargeline from a secondary side of the main relief valve 320.

The hydraulic fluid is supplied to the PTO clutch mechanism oilhydraulic circuit 300 d from a drain port of the main relief valve 320.

Reference numerals 331 and 332 in FIG. 2 denote a selector valve and anaccumulator which are provided to the PTO clutch mechanism oil hydrauliccircuit 300 d, respectively, and which are inserted into a thick-walledportion of the case member 10 (see FIG. 4).

In the power-dividing device 1A with this structure, the followingeffects can be obtained in addition to the above various effects.

In other words, the power-dividing device 1A is formed in such a mannerthat the PTO shaft 31 is disposed below the input shaft 20; the inputshaft 20 and the PTO shaft 31 are coupled to each other by the powertransmission mechanism 50; and the power is transmitted from the powertransmission mechanism 50 to the first pump shaft 61 a and the secondpump shaft 61 b.

With this structure, the driving power from the driving source 150 canreliably and readily be divided or split and output into a main powertransmission path including the pump units 60 a and 60 b and anauxiliary power transmission path including the PTO unit 30.

Moreover, with the above structure, a vertical distance between the PTOshaft 31 and the input portion of the ground work machine 140 can besuppressed while suppressing a vertical distance between the input shaft20 and the output portion of the driving source 150.

It is therefore possible to carry out, without difficulty, the powertransmission between the input shaft 20 and the output portion of thedriving source 150 and the power transmission between the PTO shaft 31and the input portion of the ground work machine 140.

This point is especially advantageous when the PTO shaft 31 is coupledto the mower 140 as in this embodiment.

In other words, there are a center discharge type shown in FIGS. 1(a)and 1(b) and a side discharge type shown in FIGS. 7(a) and 7(b), ingeneral, as a discharging structure of the mower 140.

The center discharge type or the side discharge type is appropriatelyselected depending on which is necessary and/or desired and heights ofthe input portions of the mowers 140 are normally different from eachother in both the types.

In the power-dividing device 1A according to this embodiment, the PTOshaft 31 is disposed below the input shaft 20 as described above.Therefore, the vertical distance between the PTO shaft 31 and the inputportion of the mower can be suppressed in both the center discharge typeand side discharge type.

It is therefore possible to advantageously apply the power-dividingdevice 1A according to this embodiment to both a vehicle having thedischarging structure of the center discharge type and a vehicle havingthe discharging structure of the side discharge type without addition ofmembers or changes.

Moreover, in this embodiment, the input shaft 20 and the PTO shaft 31are respectively disposed substantially in the same position in thevehicle width direction with respect to the output portion of thedriving source 150 and the input portion of the mower 140. Therefore,the power transmission therebetween can be carried out more readily.

Although the counter shaft 53 of the power transmission mechanism 50 ispositioned substantially in the same position in the vehicle widthdirection as the input shaft 20 and the PTO shaft 31 in this embodiment,the invention is of course not limited thereto.

For example, as shown in FIG. 8(a), the counter shaft 53 may bedisplaced to a position on a first side in the vehicle width directionwith respect to the input shaft 20 and the PTO shaft 31.

Although the first pump unit 60 a and the second pump unit 60 b areseparately disposed on the first side and the second side of the casemember 10 along the vehicle back and forth direction in this embodiment,it is also possible to couple the first and second pump units 60 a and60 b to the same side of the case member 10 in the vehicle back andforth direction as shown in FIG. 8(b).

Although the input shaft 20, the first and second pump shafts 61 a and61 b, and the PTO shaft 31 are in series in the power transmittingdirection in the embodiment shown in FIGS. 6, 8(a) and 8(b), instead, itis also possible that the “power transmission path from the input shaft20 to the pump shafts 61 a and 61 b” and the “power transmission pathfrom the input shaft 20 to the PTO shaft 31” are in parallel (see FIG.9). It is needless to say that the first and second hydraulic pump units60 a and 60 b can separately be disposed on the first side and thesecond side of the case member 10 in the vehicle back and forthdirection when the power transmission path from the input shaft 20 tothe pump shaft 61 and the power transmission path from the input shaft20 to the PTO shaft 31 are in parallel.

Although the first and second pump units 60 a and 60 b are coupled tothe case member 10 in this embodiment, instead, it is also possible toaccommodate the first and second pump unit main bodies 63 a and 63 b inthe case member 10.

Although the charge pump 90 is driven by the input shaft 20 in thisembodiment, instead, it is also possible that the pump shaft of one ofthe first and second pump units 60 a and 60 b has such a length as toproject outward from the corresponding center section 64 a or 64 b; thecharge pump 90 is attached to the center section to cover the projectingend portion; and the charge pump 90 is driven by the projecting endportion.

In this alternative form, although the first and second pump units 60 aand 60 b cannot be formed of the same structures, it is possible tosupply pressure oil from the charge pump to the charge oil path of thecenter section provided with the charge pump without any conduit tothereby make the conduit for the charge line unnecessary.

Embodiment 2

Another embodiment of the power-dividing device according to one aspectof the invention will be described below with reference to theaccompanying drawings.

FIG. 10 is a partial vertical sectional side view of a power-dividingdevice 1B according to this embodiment.

In the figures, members similar or corresponding to those in the firstembodiment are provided with the same reference numerals to omitdescription of the members.

As shown in FIG. 10, the power-dividing device 1B according to thisembodiment has two PTO shafts (a mid PTO shaft 31M and a rear PTO shaft31R).

Specifically, the power-dividing device 1B has a power transmissionmechanism 50B instead of the power transmission mechanism 50 and has aPTO unit 30B instead of the PTO unit 30 in the power-dividing device 1Aaccording to the first embodiment.

The power transmission mechanism 50B includes the drive-side gear 51(not shown in FIG. 10), the counter gear 52, the counter shaft 53, thedriven-side gear 54, a PTO power transmission shaft 55 for supportingthe driven-side gear 54 in a relative rotatable manner, a directionselector shaft 57 operatively connected to the PTO power transmissionshaft 55 through appropriate power transmission members 56 (powertransmission gears 56 a and 56 b in the form shown in the figures), amid PTO drive-side member 58M and a rear PTO drive-side member 58Rsupported on the direction selector shaft 57 so as to be rotatable withrespect to the direction selector shaft 57, a mid PTO driven-side member59M non-rotatable with respect to the mid PTO shaft 31M while beingengaged with the mid PTO drive-side member 58M, a rear PTO driven-sidemember 59R non-rotatable with respect to the rear PTO shaft 31R whilebeing engaged with the rear PTO drive-side member 58R, a sleeve 85supported on the direction selector shaft 57 so as to be non-rotatablewith respect to the direction selector shaft 57 and so as to bepositioned between the mid PTO drive-side member 58M and the rear PTOdriven-side member 59R, and a selector slider 86 supported on the sleeve85 so as to be non-rotatable and axially slidable with respect to thesleeve 85.

Spline is formed on an outer peripheral face of an end portion of themid PTO drive-side member 58M close to the sleeve 85.

Similarly, splines with substantially the same pitch are formed on anouter peripheral face of an end portion of the rear PTO drive-sidemember 58R close to. the sleeve 85.

Further, splines with substantially the same pitch are formed on anouter peripheral face of the sleeve 85.

On an inner peripheral face of the selector slider 86, splines to beengaged with the splines of the mid PTO drive-side member 58M, the rearPTO drive-side member 58R and the sleeve 85 are formed.

Specifically, the selector slider 86 can be positioned at (1) a midoutput position to connect only the mid PTO drive-side member 58M withthe direction selector shaft 57, (2) a both output position to connectboth the mid PTO drive-side member 58M and the rear PTO drive-sidemember 58R with the direction selector shaft 57, and (3) a rear outputposition to connect only the rear PTO drive-side member 58R with thedirection selector shaft 57, along an axial direction of the directionselector shaft 57.

Operation of the selector slider 86 by moving is carried out by anappropriate operating mechanism such as a shift fork (not shown).

The PTO unit 30B includes the mid PTO shaft 31M, the rear PTO shaft 31R,and a PTO clutch mechanism 40B for selectively engaging/interruptingpower transmission from the driven-side gear 54 to the PTO powertransmission shaft 55.

The PTO clutch mechanism 40B has substantially the same structure as thePTO clutch mechanism 40 in the first embodiment except that the PTOclutch mechanism 40B is supported on the PTO power transmission shaft55.

Therefore, detailed description of the PTO clutch device 40B will not bemade.

According to this embodiment, in addition to the effects in the firstembodiment, the auxiliary power transmission path can be divided orsplit and output into two routes.

Therefore, if a second work device such as a fan for forcibly sendinglawn debris which has been sent from the mower 140 through the reardischarge duct 145 (see FIGS. l(a) and l(b)) into a grass collection bagdisposed at the rear of the vehicle frame is provided in addition to thefirst work device such as the mower 140, it is possible to readily takeout the driving power for the second work device.

Embodiment 3

A preferred embodiment of an axle-driving device according to anotheraspect of the invention will be described below with reference to theaccompanying drawings.

An axle-driving device 3 according to the invention includes a motorunit forming a non-stepwisely changeable transmission in cooperationwith the driving actuator for each drive axle so as to independentlydrive each the drive axle at a stepwisely changeable speed.

In this embodiment, a case where hydraulic pump units are used as thedriving actuators and hydraulic motor units forming HSTs in cooperationwith the hydraulic pump units are used as the motor units will bedescribed as an example. However, the axle-driving device according tothe invention also includes a form having electric motor units as themotor units. When the electric motor units are used, generators or thelike are used as the driving actuators.

First, one example of a vehicle to which the axle-driving device 3according to this embodiment can be applied will be described.

FIGS. 11 to 13 are a schematic side view, a schematic plan view and aschematic back view of the vehicle 500 to which the axle-driving device3 according to this embodiment is applied, respectively. FIGS. 14 and 15are oil hydraulic circuit diagrams of the vehicle 500, respectively.

As shown in FIGS. 11 to 15, the vehicle 500 includes a body frame 110having a pair of main frames 111 disposed along a back and forthdirection of the vehicle, an engine 150 supported on the body frame 110,a power-dividing device 1C to which output from the engine 150 is inputthrough a flywheel 530, a pair of drive wheels 120, a pair of first andsecond drive axles 121 a and 121 b coupled to the pair of drive wheels120, respectively, so as to be non-rotatable with respect to the drivewheels 120, and first and second axle-driving devices 3 a and 3 baccording to this embodiment formed to be able to independently drivethe first and second drive axles 121 a and 121 b.

In this embodiment shown in the figures, in addition to the abovestructure, the vehicle 500 includes caster wheels 130 supported at afront portion of the body frame 110 and a mower 140 disposed between thecaster wheels 130 and the drive wheels 120 in the back and forthdirection of the vehicle.

As shown in FIGS. 11 to 13, the engine 150 is supported in avibration-preventing manner on the pair of main frames 111 throughvibration-preventing rubbers 521 in a position behind the drive axles121.

In the embodiment shown in the figures, the engine 150 is supported onthe pair of main frames 111 through the vibration-preventing rubbers 521in front, rear, left and right four positions.

FIGS. 16 and 17 are a developed plan view and a back view of thepower-dividing device 1C, respectively.

As shown in FIGS. 16 and 17, the power-dividing device IC includes acase member 610, an input shaft 20 supported by the case member 610 soas to be operatively connected to the engine 150 through the flywheel530 and a power transmission shaft 80 having a universal joint, firstand second hydraulic pump units 60 a and 60 b coupled to and supportedby the case member 610, a PTO unit 30 accommodated in the case member610, and a power transmission mechanism 50 for transmitting power fromthe input shaft 20 to the first and second hydraulic pump units 60 a and60 b and the PTO unit 30.

The first and second hydraulic pump units 60 a and 60 b form first andsecond HSTs in cooperation with first and second hydraulic motor unitswhich will be described later, respectively.

In other words, as shown in FIGS. 14 and 15, the first hydraulic pumpunit 60 a and the first hydraulic motor unit are fluid-connected by flowpaths such as a pair of conduits so as to form a closed circuit and atleast one of the first hydraulic pump unit 60 a and the first hydraulicmotor unit is of a variable displacement type.

Similarly, the second hydraulic pump unit 60 b and the second hydraulicmotor unit are fluid-connected by flow paths such as a pair of conduitsso as to form a closed circuit and at least one of the second hydraulicpump unit 60 b and the second hydraulic motor unit is of a variabledisplacement type.

In this embodiment, the first and second hydraulic pump units 60 a and60 b are of the variable displacement type and the first and secondhydraulic motor units which will be specifically described later are ofa fixed displacement type.

In this embodiment, the first and second pump units 60 a and 60 b areseparately disposed on front and rear faces of the case member 610.

Specifically, as shown in FIGS. 16 and 17, each of the first and secondhydraulic pump units 60 a and 60 b includes a pump shaft 61 operativelyconnected to the input shaft 20, a piston 63(1) for rotating about anaxis of the pump shaft 61 and reciprocate along the axis of the pumpshaft 61 as the pump shaft 61 rotates about the axis, a cylinder block63(2) which houses the piston 63(1) in a reciprocatable manner and whichrotates with the piston 63(a), an output adjusting member 63(3) fordetermining a stroke length of the piston 63(1) according to a slantingposition to change a suction/discharge rate by the piston 63(1), acontrol shaft 69 coupled to the output adjusting member 63(3) so as tobe able to control the slanting position of the output adjusting member63(3) from outside, a pump case 62 having an opening 62(1) into whichthe cylinder block 63(2), the piston 63(1) and the output adjustingmember 63(3) can be inserted to accommodate them, and a center section64 which supports the cylinder block 63(2) in a rotatable manner andwhich is coupled to the pump case 62 so as to close the opening 62(1).

The pistons 63(1), the cylinder blocks 63(2) and the output adjustingmembers 63(3) form the first and second hydraulic pump main bodies 63 aand 63 b in the first embodiment.

In the form shown in the figures, back face sides 62(2) of the first andsecond hydraulic pump units 60 a and 60 b on opposite sides to theopenings 62(1) in the pump cases 62 are coupled to the case member 610,respectively.

The PTO unit 30 includes a PTO shaft 31 supported by the case member 610so that a first end portion of the shaft 31 extends outward, adrive-side member 40 a operatively connected to the input shaft 20, adriven-side member 40 d supported on the PTO shaft 31 so as to benon-rotatable with respect to the PTO shaft 31, and a hydraulic clutchdevice 40 for engaging/interrupting power transmission from thedrive-side member 40 a to the driven-side member 40 d.

In the embodiment shown in the figures, the PTO unit 30 includes ahydraulic braking device 45 for releasing/applying a braking force fromand to the PTO shaft 31 in synchronization with engagement/interruptionby the hydraulic clutch device 40.

The power transmission mechanism 50 includes an input gear (drive-sidegear) 51 supported on the input shaft 20 so as to be non-rotatable withrespect to the input shaft 20, a pump gear (counter gear) 52 which issupported on the respective pump shafts 61 of the first and secondhydraulic pump units 60 a and 60 b through the counter shaft 53 so as tobe non-rotatable with respect to the pump shafts 61 and which is engagedwith the input gear 51, and a PTO gear (driven-side gear) 54 provided tothe drive -side member 40 a in the PTO unit 30 and engaged with theinput gear 51.

In other words, in the embodiment shown in the figures, as shown in FIG.17, the power transmission mechanism 50 includes a hydraulic pump pathfor transmitting power from the input shaft 20 to the first and secondhydraulic pump units 60 a and 60 b and a PTO path for transmitting powerfrom the input shaft 20 to the PTO unit 30.

The power-dividing device IC shown in the figures includes a charge pumpunit 90 operatively connected to the input shaft 20 in addition to theabove structure.

The charge pump unit 90 is formed to supply hydraulic fluid to thehydraulic clutch device 40 and the hydraulic braking device 45 in thePTO unit 30, the first and second HSTs, and other hydraulic mechanismsprovided to the vehicle 500.

Next, the first axle-driving device 3 a will be described.

The second axle-driving device 3 b and the first axle-driving device 3 ahave symmetric structures with respect to a fictitious central verticalplane P along a longitudinal direction of the vehicle (see FIG. 13).Therefore, the following description of the first axle-driving device 3a is also applied to the second axle-driving device 3 b.

FIGS. 18 to 20 are a vertical sectional back view, a plan view and anexploded perspective view of the first axle-driving device 3 a,respectively.

The first axle-driving device 3 a includes a first axle case 3010 a forsupporting the corresponding first drive axle 121 a in a rotatablemanner about its axis, a first hydraulic motor unit 3020 a coupled toand supported by the axle case 3010 a, a first reduction powertransmission unit 3040 a for transmitting power from the first hydraulicmotor unit 3020 a to the first drive axle 121 a with reducing a speed, afirst brake unit 3050 a capable of directly or indirectly applying abraking force to the first drive axle 121 a, and a first support member3070 a for coupling and supporting the first axle case 3010 a to and bythe body frame 110.

As shown in FIGS. 18 and 19, the first axle case 3010 a is constructedto be connected with one of the pair of main frames 111 (the first mainframe 111 a) on an outside surface thereof in the vehicle widthdirection and support the first drive axle 121 a.

In other words, as shown in FIG. 13, the first and second axle cases3010 a and 3010 b are respectively positioned outside the first andsecond main frames 111 a and 111 b in the vehicle width direction tothereby obtain a free space between the first and second main frames 111a and 111 b.

With this structure, it is easy to change specifications between acenter discharge type in which a discharge duct 145 for the mower 140 isdisposed between the pair of drive axles 121 a and 121 b and othertypes.

As shown in FIG. 18, the first axle case 3010 a includes an outer wall3011 for supporting the first drive axle 121 a in a rotatable mannerabout its axis and an inner wall 3013 separated inward in the vehiclewidth direction from the outer wall 3011 so that an inner end portion ofthe first drive axle 121 a is positioned between the outer wall 3011 andthe inner wall 3013.

In other words, an accommodating space 3010S is defined by the outerwall 3011 and the inner wall 3013 in the first axle case 3010 a, and theinner end portion of the first drive axle 121 a is positioned in theaccommodating space 3010S of the axle case 3010.

In this embodiment, the first axle case 3010 a includes an outer member3012 having the outer wall 3011 and an inner member 3014 having theinner wall 3013, and the outer member 3012 and the inner member 3014 aredetachably coupled to each other through fastening members such asbolts.

The first hydraulic motor unit 3020 a is fluid-connected to the firsthydraulic pump unit 60 a through the flow paths such as a pair ofconduits to form the closed circuit and forms the first HST incooperation with the first hydraulic pump unit 60 a as described above.

The first hydraulic motor unit 3020 a includes a motor shaft 3021supported by the inner wall 3013 in a rotatable manner about its axis sothat an outer end portion of the motor shaft 3021 in the vehicle widthdirection is positioned in the accommodating space in the axle case 3010a, and a hydraulic motor main body 3031 a coupled to and supported bythe inner wall 3013 from outside as shown in FIG. 18.

The hydraulic motor main body 3031 a includes a motor case 3032 coupledto the inner wall 3013 of the axle case 3010 a and open at an end faceopposite to the inner wall 3013, a center section 3033 coupled to themotor case 3032 so as to close the opening of the motor case 3032, acylinder block 3034 supported by the center section 3033 so as to berotatable about the motor shaft 3021 and so as to be positioned in aninner space defined by the motor case 3032 and the center section 3033,a piston 3035 accommodated in a reciprocatable manner in the cylinderblock 3034, and a swash plate 3036 for restricting a range ofreciprocation of the piston 3035.

In the center section 3033, oil paths 3101 forming a portion of flowpaths 3100 a between the corresponding first hydraulic motor unit 3032 aand the first hydraulic pump unit 60 a are formed. The oil paths 3101are open to the outside at first end portions thereof and communicatewith the cylinder block 3034 at second end portions thereof (see FIG.15).

By hydraulic fluid supplied and discharged through the oil paths 3101,the piston 3035 reciprocates in the cylinder block 3034 and rotatesabout the motor shaft 3021 and, as a result, the cylinder block 3034 andthe motor shaft 3021 rotate about the axis of the motor shaft 3021.

The first reduction power transmission unit 3040 a includes an outputgear 3041 supported on an outer end portion of the motor shaft 3021 inthe vehicle width direction so as to be non-rotatable with respect tothe motor shaft 3021, a first intermediate gear 3042 engaged with theoutput gear 3041, an intermediate shaft 3043 provided with the firstintermediate gear 3042 and supported by the axle case 3010 a so as to bepositioned above the motor shaft 3021, a second intermediate gear 3044provided to the intermediate shaft 3043, and a final gear 3045 engagedwith the second intermediate gear 3044 and supported on an inner endportion of the first drive axle 121 a in the vehicle width direction soas to be non-rotatable with respect to the first drive axle 121 a. Thethus arranged unit 3040 a can reduce a speed of and transmit drivingoutput from the motor shaft 3021 to the first drive axle 121 a.

As described above, in the first axle-driving device 3 a according tothis embodiment, the first reduction power transmission unit 3040 a isprovided between the first hydraulic motor unit 3020 a and thecorresponding first drive axle 121 a and, as a result, thehighly-reliable, low-torque and high-speed rotation motor can be used asthe first hydraulic motor unit 3020 a.

Such a low-torque and high-speed rotation motor has advantages that itcan be made compact; a leak amount of the hydraulic fluid is small; andvolumetric efficiency is high over a high-torque and low-speed rotationmotor.

The first brake unit 3050 a selectively applies the braking force to theintermediate shaft 3043 to thereby independently apply the braking forceto the corresponding first drive axle 121 a.

The first brake unit 3050 a is disposed by utilizing an idle space abovethe first hydraulic motor unit 3020 a.

Specifically, the intermediate shaft 3043 is supported by the axle case3010 a so that an inner end portion of the intermediate shaft 3043 inthe vehicle width direction extends outward. The first brake unit 3050 ais formed to be able to act on the inner end portion of the intermediateshaft 3043 in the vehicle width direction.

In this embodiment, the inner wall 3013 of the axle case 3010 a has arib 3015 extending inward in the vehicle width direction so as tosurround the inner end portion of the intermediate shaft 3043 in thevehicle width direction. The first brake unit 3050 a is mounted to therib 3015.

More specifically, the first brake unit 3050 a includes a rotary member3051 supported on the inner end portion of the intermediate shaft 3043in the vehicle width direction so as to be non-rotatable with respect tothe intermediate shaft 3043, a fixed member 3052 supported by the axlecase 3010 a, a friction braking device 3053 for operatively applying afriction force between the rotary member 3051 and the fixed member 3052,and an operating arm 3054 for actuating the friction braking device 3053by operation from outside.

The friction braking device 3053 includes a rotating-side friction disc5303 a supported by the rotary member 3051 so as to be non-rotatablewith respect to the rotary member 3051, a fixed-side friction disc 3053b supported by the fixed member 3052 so as to be non-rotatable withrespect to the fixed member 3052 and so as to face the rotating-sidefriction disc 3053 a, and an actuating member 3053 c for bringing therotating-side friction disc 3053 a and the fixed-side friction disc 3053b into frictional engagement with each other based on operation of theoperating arm 3054 (see FIG. 15).

In this embodiment, a ball cam mechanism is employed as the actuatingmember 3053 c. The actuating member 3053 c bring the rotating-sidefriction disc 3053 a and the fixed-side friction disc 3053 b intofrictional engagement with each other by a swinging action of the arm3054 about a pivot axis parallel to the intermediate shaft 3043.

Various structures may be employed as the first support member 3070 a aslong as the structure can couple and support the axle case 3010 a to andby the first main frame 111 a.

As shown in FIGS. 18 to 20, in this embodiment, a mounting stay 3071having a proximal end portion coupled to the first main frame 111 a anda distal end portion supporting the axle case 3010 a is used as thesupport member 3070 a.

The mounting stay 3071 is formed so that a surrounded space in which thefirst hydraulic motor unit 3020 a is positioned and at least an upperside of which is open is formed between the inner wall 3013 of the axlecase 3010 a and the first main frame 111 a.

Specifically, the mounting stay 3071 includes a pair of side wallportions 3072 having proximal end portions coupled to the first mainframe 111 a and a pair of mounting portions 3073 extending from distal(outer) end portions of the pair of side wall portions 3072 toward eachother, and having an opening which is formed between opposed endportions of the mounting portions 3073 and through which the firsthydraulic motor unit 3020 a and the first brake unit 3050 a can beinserted. The thus mounting stay 3071 forms the surrounded space whichis defined by the pair of side wall portions 3072, the mounting portions3073 and the first main frame 111 a as shown in FIGS. 19 and 20.

By provision of the mounting stay 3071 with such a structure, it ispossible to mount an assembly of the first axle case 3010 a, the firsthydraulic motor unit 3020 a, the first reduction power transmission unit3040 a and the first brake unit 3050 a to the mounting stay 3071 fromoutside in the vehicle width direction in the state where the mountingstay 3071 is mounted to the body frame 110. As a result, workability inassembly of the first axle-driving device 3 a to the body frame 110 canbe improved.

Reference numerals 3074 and 3075 in FIG. 20 denote reinforcing platesand fastening bolts, respectively.

In the first axle-driving device 3 a with such a structure, thefollowing effects can be obtained in addition to the above variouseffects.

In other words, in this embodiment, as is well shown in FIG. 18, thefirst hydraulic motor unit 3020 a is coupled to the inner wall 3013 ofthe axle case 3010 a so that at least a portion of the first hydraulicmotor unit 3020 a overlaps with the final gear 3045 when viewed alongthe axial direction of the first drive axle 121 a.

Therefore, without upsizing the first axle case 3010 a, the firsthydraulic motor unit 3020 a can be coupled to and supported by the firstaxle case 3010 a.

Moreover, the first brake unit 3050 a and the first hydraulic motor unit3020 a are separately disposed on upper and lower sides in thesurrounded space in the mounting stay 3071.

In other words, the first brake unit 3050 a is coupled to the inner wall3013 of the axle case 3010 a by utilizing the idle space above the firsthydraulic motor unit 3020 a in the surrounded space in the mounting stay3071.

With this structure, because the first brake unit 3050 a and the firsthydraulic motor unit 3020 a are not arranged in parallel with each otherin the vehicle width direction, it is possible to obtain a free space aslarge as possible between the pair of drive wheels 120 withoutincreasing a distance between the pair of drive wheels 120.

In this embodiment, the engine 150 is disposed at an upper portion andthe center discharge duct 145 in the mower 140 is disposed at a lowerportion in the free space between the pair of drive wheels (see FIG. 13and the like).

In this embodiment, the first brake unit 3050 a is disposed in thesurrounded space which is defined by the mounting stay 3071 and theupper side of which is open as described above. Therefore, as shown inFIGS. 18 to 20, the operating arm 3054 in the brake unit 3050 a can beoperated through the upper opening of the surrounded space to therebysimplify a linkage for linking the operating arm 3054 with and to aparking lever 591 and a brake pedal 592 provided in the vicinity of thedriver's seat.

Further, in this embodiment, as shown in FIGS. 18 and 19, the first endportions of the oil paths 3101 in the center section 3033 are formed tobe oriented upward at a position between the operating arm 3054 in thebrake unit 3050 a and the first main frame 111 a in the vehicle widthdirection.

In other words, the first end portions of the oil paths 3101 formingconnection portions to the driving actuator (hydraulic pump unit 60 a inthis embodiment) are oriented upward while avoiding the first brake unit3050 a in the vehicle width direction.

Therefore, a connecting member (conduit such as high-pressure conduit)between the driving actuator and the hydraulic motor unit can be readilyconnected to the connection portion (the first end portions of the oilpaths 3101 in this embodiment) through the upper opening of thesurrounded space.

Lastly, the oil hydraulic circuit of the vehicle 500 to which theaxle-driving devices 3 a and 3 b according to this embodiment areapplied will be described with reference to FIGS. 14 and 15.

As shown in FIG. 14, the charge pump unit 90 suctions oil from anexternal reservoir tank 800 through a filter 810. Then, pressure oilfrom the charge pump unit 90 is supplied to charge circuits 900 a and900 b of the first and second HSTs, a working machine lifting/loweringoil hydraulic circuit 910, and the PTO unit engaging/interruptingcircuit 920, respectively, at predetermined pressures.

The pressure oil is supplied to the charge circuits 900 a and 900 bthrough charge ports 820 provided to back faces of the respective centersections 64 in the first and second hydraulic pump units 60 a and 60 b(see FIGS. 14 and 16). The pressure oil is supplied to the PTO unitengaging/interrupting circuit 920 through a PTO port 830 provided to thecase member 610 (see FIGS. 14 and 16).

Hydraulic fluid leaking from the first and second hydraulic pump mainbodies 63 a and 63 b is gathered into the case member 610 through drainoil paths 840 formed in the pump case 62 and the case member 610 andthen returned to the external reservoir tank 800 through an externalconduit 850 as shown in FIGS. 14 and 16.

Hydraulic fluid leaking from the first and second hydraulic motor mainbodies 3031 a and 303 lb is returned to the external reservoir tank 800through drain ports 860 provided to the respective motor cases 3032 orthe respective center sections 3033 in the first and second hydraulicmotor units 3020 a and 3020 b and the corresponding external conduits870 a and 870 b.

This specification is by no means intended to restrict the presentinvention to the preferred embodiments set forth therein. Variousmodifications to the power-dividing device, as well as the axle-drivingdevice as described herein, may be made by those skilled in the artwithout departing from the spirit and scope of the present invention asdefined in the appended claims.

1-17. (canceled)
 18. An axle-driving device comprising: an axle caseincluding an outer wall supporting a drive axle in a rotatable mannerabout its axis and an inner wall separated inward in a vehicle widthdirection from the outer wall so that an inner end portion of said driveaxle in the vehicle width direction is positioned between said outerwall and the inner wall; a motor unit which forms a non-stepwiselychangeable transmission in cooperation with an actuator disposed at adistance, the motor unit including a motor shaft supported by the innerwall in a rotatable manner about its axis so that an outer end portionof the motor shaft in the vehicle width direction is positioned in aaccommodating space in said axle case, and a motor main body supportedby said inner wall; a reduction power transmission unit which includesan output gear supported on the outer end portion of said motor shaft inthe vehicle width direction so as to be non-rotatable with respect tothe motor shaft, a final gear supported on the inner end portion of saiddrive axle in the vehicle width direction so as to be non-rotatable withrespect to the drive axle, and a gear train for reducing a speed of andtransmitting power from said output gear to said final gear andincluding an intermediate shaft supported by said axle case so as to bepositioned above said motor shaft; and a brake unit for selectivelyapplying a braking force to said intermediate shaft based on operationfrom outside, in which said motor unit is disposed so that at least aportion of said motor unit overlaps with said final gear when viewedalong an axial direction of said drive axle, and said brake unit issupported by the inner wall of said axle case so as to be positionedabove said motor unit.
 19. An axle-driving device as set forth in claim18, in which said brake unit is disposed so that at least a portion ofthe brake unit overlaps with said hydraulic motor unit in plan view. 20.An axle-driving device as set forth in claim 18, further comprising: amounting stay having a proximal end portion coupled to a body frame anda distal end portion supporting said axle case, in which said mountingstay is formed so as to define a surrounded space in which said motorunit is positioned and at least an upper side of which is open betweenthe inner wall of said axle case and said body frame, said brake unitincludes a rotary member supported on said intermediate shaft in anon-rotatable manner, a fixed member supported by said axle case, afriction braking device which has a pair of friction discs respectivelysupported by said rotary member and said fixed member in a non-rotatablemanner and which selectively applies a braking force to said rotarymember based on operation from outside, and an operating arm foroperating said friction braking device by swinging about a pivot axisdisposed in parallel to said intermediate shaft, and said operating armcan be operated from the upper opening of said surrounded space.
 21. Anaxle-driving device as set forth in claim 20, in which said motor unitis formed so that a connection portion to said actuator is orientedupward at a position between said operating arm of said brake unit andsaid body frame.
 22. An axle-driving device as set forth in claim 21, inwhich said actuator is a hydraulic pump unit, said motor unit is ahydraulic motor unit fluid-connected to said hydraulic pump unit througha flow path so as to form an HST in cooperation with the hydraulic pumpunit, and said hydraulic motor unit has a center section formed with anoil path which forms a portion of said flow path and a first end portionof which forms said connection portion to the actuator.
 23. A vehiclecomprising: a body frame including a pair of main frames disposed alonga vehicle back and forth direction; an engine supported on the bodyframe; a power-dividing device including a pair of hydraulic pump unitsoperatively connected to an output portion of the engine; a pair ofdrive axles; and a pair of axle-driving devices respectively andindependently driving the pair of drive axles, in which each of saidpair of axle-driving devices includes an axle case, a hydraulic motorunit, a reduction power transmission unit and a brake unit, said axlecase has an outer wall supporting the corresponding drive axle in arotatable manner and an inner wall separated inward in a vehicle widthdirection from said outer wall so that an inner end portion of the driveaxle in the vehicle width direction is positioned between the outer walland the inner wall, the axle case being supported by the correspondingmain frame, said hydraulic motor unit is fluid-connected to thecorresponding hydraulic pump unit through a flow path so as to form anHST, the hydraulic motor unit including a motor shaft supported by saidinner wall in a rotatable manner so that an outer end portion of themotor shaft in the vehicle width direction is positioned in anaccommodating space in said axle case and a motor main body supported bysaid inner wall, a reduction power transmission unit includes an outputgear supported on an outer end portion of said motor shaft in thevehicle width direction in a non-rotatable manner, a final gearsupported on an inner end portion of said drive axle in the vehiclewidth direction in a non-rotatable manner, and a gear train for reducinga speed of and transmitting power from said output gear to said finalgear, the gear train including an intermediate shaft supported by saidaxle case so as to be positioned above said motor shaft, said brake unitis formed to selectively apply a braking force to said intermediateshaft based on operation from outside, said hydraulic motor unit isdisposed so that at least a portion of the motor unit overlaps with saidfinal gear when viewed along an axial direction of said drive axle, andsaid brake unit is supported by the inner wall of said axle case so asto be positioned above said hydraulic motor unit.
 24. A vehicle as setforth in claim 23, in which each of said pair of axle-driving devicesfurther includes a mounting stay having a proximal end portion coupledto the corresponding main frame and a distal end portion supporting saidaxle case, said mounting stay is formed so as to define a surroundedspace in which said hydraulic motor unit is positioned and at least anupper side of which is open between the inner wall of said axle case andsaid corresponding main frame, said brake unit includes a rotary membersupported on said intermediate shaft in a non-rotatable manner, a fixedmember supported by said axle case, a friction braking device which hasfriction discs respectively supported by said rotary member and saidfixed member in a non-rotatable manner and which selectively applies abraking force to said rotary member based on operation from outside, andan operating arm for operating said friction braking device by swingingabout a pivot axis disposed in parallel to said intermediate shaft, andsaid operating arm can be operated from the upper opening of saidsurrounded space.
 25. A vehicle as set forth in claim 24, in which saidhydraulic motor unit has a center section formed with an oil pathforming a portion of said flow path between said hydraulic pump unit andthe hydraulic motor unit, and said oil path opens upward at a positionbetween said operating arm in said brake unit and said main frame.